Temperature sensitive normally open relay



April 26, 1960 M. D. PATRICHI 2,934,525

TEMPERATURE SENSITIVE NORMALLY OPEN RELAY Filed Oct. so, 1958 Q\\F Z2 INVENIOR.

MHA/ 0. P4 TR/CH/ BY u Armin/6K5 United States Patent TEMPERATURE SENSITIVE NORMALLY OPEN RELAY Mihai D. Patrichi, Chatsworth, Calif., assignor to Networks Electronic Corporation, Van Nuys, Caliil, a corporation of California Application October 30, 1958, Serial No. 770,714 13 Claims, (Cl. 200 -117) This application is a continuation in part of my pending application S.N. 739,932, filed June 4, 1958, for Electrical Component With Improved Metal to Glass End Sealing Mechanism, and my earlier patent application SN. 615,981, filed October 15, 1956, for Electrical Resistors and the Like, now abandoned, said application S.N. 739,932 being a continuation in part of said earlier application.

This invention relates to temperature sensitive relays in general and in particular to a normally open temperature sensitive relay of relatively small proportions, embodying in general, an envelope structure consisting in a tubular glass barrel and headers sealing the respective ends of said barrel, and pairs of terminals extending through and sealed in the respective headers and circuit making parts operating within said envelope, and has as its general object to provide an improved temperature sensitive normally open relay of this type, especially suitable for use under high requirement conditions of wide temperature change and heavy vibration and acceleration forces, as in rocket and jet propelled missiles and vehicles, and in other high demand structures.

A particular object is to provide such a relay embodying an improved construction particularly characterized by extreme ruggedness and resistance to the eifects of vibration, shock, wide ranges of temperature and moisture.

A further object is to provide such a relay, embodying a compact but efficient and dependable arrangement of relay parts within a cylindrical tubular envelope of small dimensions.

Other objects and advantages will become apparent in the ensuing specification and appended drawing in which:

.Fig. 1 is a side view of a relay embodying the invention;

Fig. 2 is an end view thereo;

Fig. 3 is a longitudinal sectional view thereof .on an enlarged scale, the internal parts being shown in ele- 'vation;

Fig. 4 is an axial sectional view thereof showing the internal parts in section;

Fig. 5 is a fragmentary sectional view on a further magnified scale showing the improved joints between metal and glass parts;

Fig. 6 is a sectional view on a still further magnified scale showing a small fragment of one of the glass to metal joints; and

Fig. 7 is a transverse sectional view taken on the line 7-7 of Fig. 4. V i

Referring now to the drawing in detail, I have shown therein, as an example of one form in which the invention may be embodied, a normally open thermal relay embodying in general an'envelope structure comprising a cylindrical barrel 12 and headers, indicated generally at 9 and 13, secured in and sealing the respective ends a of the barrel 12 to provide therewith a sealed envelope; 1 together with relay parts within the envelope, including a plunger 31 slidably mounted within the barrellZ, a ,coil spring 32 for projecting the plunger to a position in 2,934,625 Patented Apr. 26, 1960 2 which a projectile contact 33 on one end of the plunge may close the circuit between a pair of normally open contacts sealed in the header 9; and a fuse element 34 anchored between the plunger 31 and a pair of anchor loops 8 mounted in the other header, whereby the plunger 31 is normally held in a retracted position but will be released upon melting of the fuse element 34 when subjected to overload, therebycausing the plunger 31 to be spring projected so that the projectile contact 33 will close the circuit between terminals 11 to which the contacts 10 are connected.

The headers 9 and 13 each include a metal mounting ring 17 of L-section, consisting in a radial flange 14 (Fig. 5) and an open collar 15 projecting axially from the inner margin of flange 14 into a respective end of barrel 12. Mounting rings 14, 15 are soldered at ,16'to the ends of barrel 12, previously covered with metalas hereinafter described, to provide a very secure pneumatically sealed connection, resistant to vibration, shocks, moisture-laden air, etc. Each header 9 and 13 includes an insulator plug 18 fused or soldered into collar 15 thereof. Pairs of terminal rods or wires 19 and 11 are fused into cylindrical bores in respective plugs 18 and project therethrough into the respective ends of the sealed chamber within the envelope. The ends of terminals 11 are formed with loops embodying transverse bends constituting the spaced relay contacts 10. The loops are disposed in parallel planes equally spaced on opposite sides of and parallel to the longitudinal axis of the relay, so as to receive between them the pointed end of the projectile contact 33 for closing the relay. Each plug 18 has two pairs of bores disposed respectively in said parallel planes, spaced apart circumferentially preferably at spacing and at equal radial spacing from the axis. Each contact loop is formed integrally on the .end of a respective terminal 11, the latter extending entirely through the plug 18 in one of the bores thereof. The loop embodies two straight parallel legs one of which is a linear extension of the terminal and the other of which is a return bend extending fully or part way through an adjacent bore of the plug and having its end embedded in the plug. Both the body of the terminal and the leg of the loop are fused to the glass walls of their respective bores, as indicated in Figs. 4'and 7. Each loop embodies the transverse bend (which may be of curved arch form as shown) bridging between and integrally joining'the two legs of the loop to constitute the contacts 10 which are disposed in substantially parallel relation, equally spaced from opposite sides of the relay axis.

Contacts 10 are slightly bowed radially outwardly from the relay axis as seen in end view (Fig. 7) so as to have a centering action against the conical nose of contact 33 as the latter is driven between the contacts by the coil spring 32. They project into the envelope to a somewhat greater length than anchor loops 8, to arrest the movement of plunger 31 at a point where contact 33 remains spaced away from header 9. Although quite stiff, contact loops 10 are of slight resiliency and provide some shock-absorbing action, thus protecting the header 9 from damage from the impact of contact 33.

An identical loop construction may be (and preferably is) utilized for the anchor loops 8, formed integrally with respective terminals 19. The respective ends of fuse element 34 are wrapped around and welded or soldered to loops 8 on the ends of terminals 19 where they project into the interior of the envelope.

The secure anchoring of both legs of each contact loop 10 and anchor loop 8- in its respective header provides a very rugged construction wherein, on the one hand, the normally open contacts 10 wil1 take the shock of impact of projectile contact 33 without unduly yielding, and wherein on the otherhand, the anchor loops 8 will sustain the tension load imposed through fuse element 34 without being pulled away from the respective header.

Barrel i2 and plugs 18 are of high temperature heatresistant glass of high lead content, such as Pyrex glass. The mounting rings 17 of headers 9 and 13 are drawn sheet metal parts, of a corrosion resistant metal, such as Kovar (an alloy of iron, nickel and cobalt) having substantially the same coefficient of thermal expansion as the glass parts. Terminals 11 and 19 are likewise preferably of Kovar metal.

Plunger 31 is of molded insulating material, preferably a thermosetting plastic material. Contact 33 is a noncorrosive metal (preferably silver) slug of generally cylindrical form, with a bullet nose and a base that is preferably flanged or headed at 35 for secure anchorage in the plunger 31 at the axis thereof. In the rear end of the plunger 31 is a cylindrical axial recess 36 which is traversed diametrically by an anchor pin 37. The bight of fuse link 34 is looped around the pin 37, and a substantial portion of the length of link 34 is received in the recess 36, thus providing adequate length in the fuse link.

The glass parts (barrel 12 and plug 18) and the metal parts (mounting rings 17) are joined to one another by strong, durable hermetically sealed joints permanently resisting leakage and mechanical breakdown (from the efiect of shocks and vibration). This is attained through the use of improved composite laminated joints indicated at 22 and 24 (Figs. and 6). Each of said joints consists in three or four separate coatings, including: a very thin molecular film of noble metal fused to the glass surface; an electro-deposited coating of a good binding metal such as copper, joined to such noble metal film; a surface (e.g. film) of noble metal upon the surface of the mounting ring 14, 15; and a film of solder interposed between the noble metal surface of the metal part and the electro-deposited coating on the glass part and bonding the same together.

In the preferred form of the invention, the mounting ring is of Kovar metal and the noble metal films on the glass part and upon the surface of the metal part are of silver.

Silver solder is used in the solder coating wherever the component is required to withstand temperatures exceeding 400 F. However, for those cases where the temperature range is below a maximum limit of approximately 400 (cg. 390 F. or under) I find that satisfac t'ory results can be obtained by utilizing a tin-lead solder of a high temperature type, i.e., having a higher melting point (higher lead content) than the solder commonly used in establishing electrical connections. Either of these solders are regarded as a high temperature solder, the silver solder having the higher range.

The joint 22 is interposed between flange 14 and an opposed end of barrel 12; and the joint 24 is interposed between the periphery of plug 18 and the internal surface of mounting ring collar 15. A joint 23, between terminals 19 and 1 1 and the bores of plugs 18, may be a plain fused metal-to-glass joint as described hereinafter.

The joints 22 are formed integrally with joints 30 of cylindrical sleeve form interposed directly between the cylindrical outer surfaces of headers 13 and the cylindrical inner surface of barrel 12 as shown.

Kovar is a preferred material for the mounting rings 17, since it is especially well matched to hard glass such as Pyrex in its expansion characteristics. Where such a metal is used, the coating of noble metal thereon is an essential element of the device. Alternatively, in some cases the metal part may be of solid noble metal, in which case the surface thereof constitutes the fourth coating.

The term molecular film as applied to the noble metal film on the glass surface is not necessarily restricted to a film of single molecule thickness. Instead, the term is intended to designate a coating having a thinness within the range of approximately .0005 inch to .005 inch.

4 As shown in Fig. 6, the several layers of each bonding joint, beginning with the layer attached to the glass surface, are arranged in the following order and indicated by the following reference characters:

(1) Noble metal (silver) film on glass surface;

(2) Electro-coating (copper) on silver film;

(3) Solder binding layer;

(4) Noble metal surface (silver electro-deposited on Kovar) on metal part.

The noble metal coatings on the metal parts and the metal films and copper coatings on the glass parts are deposited on the surfaces of the respective parts prior to assembly into the finished component. In the coating process for the glass parts, the latter are preliminarily prepared by thorough cleansing. If they are dirty, they may be first Water washed (eg. in a detergent solution) and rinsed or may be preliminarily washed in methanol. Two main cleaning steps are then performed namely (a) soaking in chromic acid solution and (b) soaking in methanol. The parts are preferably rinsed between the chromic acid and methanol baths. The parts are then dried.

As a second main step following the cleaning step, a silver paste paint (e.g. a mixture of powdered silver in 40% toluene) is applied by brushing or dipping, to the areas of the glass that are to be fused to the metal parts.

As a third step, the coated parts are heat treated (e.g. in an electric oven) to anneal the glass parts and fuse the silver coatings thereto, temperatures in the range of 1140 F. to 1150 F. being reached. For example, in a preferred practice of the process, the parts are cured for three hours at 1150 F. to fully vaporize and dissipate all traces of the toluene carrier, and to leave the silver particles in the form of a continuous (1) film of silver -metal which is fused to the glass surfaces. At the conclusion of the curing operation, the parts are allowed to cool slowly to room temperature to avoid shattering of the glass.

As a fourth step in the process, silvered surfaces (4) of the glass parts are coated with copper by an electroplating step. In the electro-plating step, substantial copper coatings (3) are built upon the glass parts, to a thickness in the range of .0005 inch to .005 inch.

In a separate series of steps, header plugs 18 are prepared by pressure molding bodies of powdered glass in the form of the plugs 18 and then sintering them to form cylindrical glass beads having the four axially extending bores described above. The terminals 11, 19 are then inserted through these bores and then are fused into the glass beads by heat treating at temperatures in the fusing range of the glass to fuse the sintered glass beads into a solid body of non-porous glass for each of the plug elements 18, with the terminals fused therein.

The plugs 18, with terminals fused therein, are then assembled within respective mounting rings 17 and are sealed therein by forming the joints 24 as described above. The headers 13 and 9 are successively assembled in the ends of the barrel 12 and joined thereto by joints 22, 30.

After the header 13 has been attached to the barrel, the assembly of internal electrical parts attached to header 9 is inserted, and the header 9 is then assembled to the open end of the barrel and is bonded thereto in the same manner as the header 19.

In attaching each header to the barrel, the header is assembled loosely in place with an interposed ring of solder, and the entire assembly is then subjected to fusing heat applied to the open end thereof to bond the header to the barrel.

The solder ring may be in the form of a thin flat washer, and may be interposed between the flange 14 and the end of barrel 12 in the loose assembly. When the solder ring melts, it will flow and spread between the surfaces of the metal and glass parts, and the portion 30 of the joint is constituted of solder flowing inwardly from between the'flange 14 and the end of the barrel and entering'the annular space 27 between collar 15 and the inner wall of the barrel 12.

An insulator grommet 38 (which may be of molded plastic material) is interposed between the end of spring 32 and header 13, for supporting the spring in coaxial relation to the relay axis.

I claim:

1. In a miniature thermal relay: an envelope comprising a tubular barrel of high temperature glass and a pair of headers closing and sealing the respective ends thereof, each of said headers comprising a cylindrical center plug of high temperature glass corresponding to that of said barrel in expansion characteristics, and a mounting ring of a metal that is matched to said glass parts in expansion characteristics, interposed between and bonded to the respective glass parts at each end of the envelope, said mounting ring being of L- section, including a fiat radial flange bonded to a respective end of said barrel, and a cylindrical collar extending from the inner margin of said flange into a respective end of said barrel and radially spaced therefrom by an annular cylindrical space; an assembly of fuse parts in one end ofsaid envelope, including a plunger slidably mounted in said barrel, a loading spring engaged under compression between said plunger and one of said headers, a first pair of terminals extending through and fused and sealed in the plug of one header, and a fuse link attached under tension between said terminals and said plunger andnormally holding the latter in a retracted position under the load of said spring; and a normally open switch comprising a second pair of terminals extending through and fused and sealed in the plug of the other header and having end portions projecting into said envelope, a pair of spaced normally open contacts attached to said projecting end portions, and a third contact carried by the opposed end of said plunger and adapted to engage between said normally open contacts to close a circuit connected to said second pair of terminals upon melting of said fuse link in response to a temperature overload thereon.

2. A relay as defined in claim 1, including muiti-layer joints interposed between said flanges and the ends of said barrel, each joint consisting in a film of noble metal fused on an end surface of said barrel, a coating of copper electro-plated on said film, a surface of noble metal on the respective flange, and a layer of high temperature solder interposed between and joined to the respective copper coating and said noble metal surface.

3. A relay as defined in claim 1, wherein said barrel is of glass having the thermal characteristicsof Pyrex,

said mounting ring is of nickel-iron alloy having the thermal expansion properties of Kovar, including multilayer joints interposed between said flanges and the ends of said barrel, each joint including a noble metal film of silver directly adhering to a respective glass surface and a noble metal surface is of silver electroplated on said flange, and a bonding layer interposed between andjoining said silver film and noble metal surface.

4. In a miniature thermal relay: an envelope comprising a cylindrical tubular barrel of high temperature glass and a pair of headers closing and sealing the respective ends thereof, each of said headers comprising a cylindrical central plug of high temperature glass and a circular mounting ring of metal including a cylindrical collar encircling andbonded to the periphery of the plug and a flange bonded to said barrel at a respective end thereof, said plug, mounting ring and barrel having substantially matched expansion characteristics; an assembly of fuse parts in one end of said envelope, including a plunger slidably mounted in said barrel, a loading spring engaged under compression between said plunger and one of said headers, a first pair of terminals extending through and fused and sealed in the plug of one header, and a fuse link attached under tension between said terminals and said plunger and normally holding the latter in a retracted goddess position under the load of said spring; the plug of the other header. having therein two pairs of circumfcrentially spaced bores extending parallel to the major axis of the relay and disposed in parallel planes equally spaced from opposite sides of said axis; and a normally open switch comprising a second pair of terminals each extending through one of the bores of one'of said pair of bores into the interior of the envelope, and a pair of loops disposed within the envelope in said parallel planes, projecting axially inwardly from the respective header and formed as integral extensions of the respective terminals of said second pair, each of said loops including a pair of substantially parallel legs, one constituting an integral linear extension of a respective terminal and the other being a return bend extending into the other bore of the respective pair of bores and havingits end embedded in said plug, and each of said loops further including a transverse bend integrally joining and bridging between the two legs of the respective loops, disposed in substantially parallel relation and equally spaced radially from opposite sides of said axis to constitute a pair of normally open contacts, and a projectile contact carried by the opposed end of said plunger at the axis thereof and adapted to engage between said normally open contacts to close a circuit connected to said second pair of terminals upon melting of said fuse link in response to a temperature overload thereon.

5. In a miniature thermal relay: an envelope comprising a tubular barrel of high temperature glass and a pair of headers closing and sealing the respective ends thereof, each of said headers comprising a central plug of high temperature glass corresponding to that of said barrel in expansion characteristics, and a mounting ring of a metal that is matched to said glass parts in expansion characteristics, interposed between and bonded to the respective glass parts at each end of the envelope; an assembly of fuse parts in one end of said envelope, including a plunger slidably mounted in said barrel, a loading spring engaged under compression between said plunger and one of said headers, a first pair of terminals extending through and fused and sealed in the plug of one header, and a fuse link attached under tension between said terminals and said plunger and normally holding the latter in a retracted position under the load of said spring; and a normally open switch comprising a second pair of terminals extending through and fused and sealed in the plug of the other header and having integralend portions projecting into said envelope and constituting a pair of spaced normally open contacts; and a third contact carried by the opposed end of said plunger at the axis thereof and adapted to engage between'said normally open contacts to close a circuit connected to said second pair of terminals upon melting of said fuse link in response to a temperature overload thereon; each mounting ring being of L-section in a radial plane, including a cylindrical collar encircling and bonded and sealed to the periphery of a respective plug, and a radial flange extending outwardly from the outer end of said collar and bonded to a respective end of said barrel, said collar being received within a respective end of said barrel.

6. A relay as defined in claim 5, wherein said collar is separated from the inner wall of said barrel by an annular cylindrical space.

7. A relay as defined in claim 9, wherein said transverse bends are centrally indented radially outwardly from said axis so as to receive said third contact with a centering action.

8. A relay as defined in claim 4, wherein said plugs are of glass originally powdered, then sintered with said bores molded therein, and then fused to solid, gas-impermeable state, fused to said terminal loop legs and sealing them in the plug.

9, In a miniature thermal relay: an envelope comprising a tubular barrel of high temperature glass and a pair of headers closing and sealing the respective ends thereof, each of said headers comprising a central plug'of high temperature glass corresponding to that of said barrel in expansion characteristics, and a mounting ring of a metal that is matched to said glass parts in expan sion characteristics, interposed between and bonded to the respective glass parts at each end of the envelope; an assembly of fuse parts in one end of said envelope, including a plunger slidably mounted in said barrel, a loading spring engaged under compression between said plunger and one of said headers, a first pair of terminals extending through and sealed in the plug of one header, and a fuse link attached under tension between said terminals and said plunger and normally holding the latter in a retracted position under the load of said spring; and a normally open switch comprising a second pair of terminals extending through and sealed in the plug of the other header and having integral end portions projecting into said envelope on axes radially spaced from the center of the plug and thence bent laterally to provide parts extending generally parallel to one another spaced from said center on opposite sides thereof, and constituting a pair of spaced normally open contacts, and a third contact carried by the opposed end of said plunger at the axis thereof and adapted to engage between said normally open contacts to close a circuit connected to said second pair of terminals upon melting of said fuse link in response to a temperature overload thereon; said integral end portions of said second pair of terminals being in the form of loops having parallel legs one of which consists in a linear extension of the respective terminal, the other leg being a return bend having its end engaging and supported by said plug.

10. In a miniature thermal relay: an envelope comprising a tubular barrel of high temperature glass and a pair of headers closing and sealing the respective ends thereof, each of said headers comprising a central plug of high temperature glass corresponding to that of said barrel in expansion characteristics, and a mounting ring of a metal that is matched to said glass parts in expansion characteristics, interposed between and bonded to the respective glass parts at each end of the envelope, said mounting ring being of L-section, including a flat radial flange bonded to a respective end of said barrel, and a cylindrical collar extending from the inner margin of said flange into a respective end of said barrel and encircling and bonded and sealed to the periphery of a respective plug; an assembly of fuse parts in one end of said envelope, including a plunger slidably mounted in said barrel, a loading spring engaged under compression between said plunger and one of said headers, a first pair of terminals extending through and sealed in the plug of one header, and a fuse link attached under tension between said terminals. and said plunger and normally holding the latter in a retracted position under the load of said spring; and a normally open switch comprising a second pair of terminals extending through and sealed in the plug of the other header and having integral end portions projecting into said envelope and constituting a pair of spaced normally open contacts, and a third contact carried by the opposed end of said plunger at the axis thereof and adapted to engage between said normally open contacts to close a circuit connected to said second pair of terminals upon melting of said fuse link in response to a temperature overload thereon.

11. A relay as defined in claim 10 wherein said pair of normally open contacts are in the form of integral loops on the ends of said second pair of terminals, each loop embodying spaced parallel legs, one constituting a linear continuation of a respective terminal extending entirely through the respective plug and the other having its end embedded in the plug.

12. A relay as defined in claim 10 wherein said plunger comprises a cylindrical body of molded synthetic resin plastic material having in one end an axial recess and a cross pin traversing said recess, said fuse link consisting in a length of fuseable wire in elongated loop form embodying spaced legs anchored at their ends to respective terminals of said first pair and a bight that is looped around said cross pin and thereby anchored to the plunger, said third contact being in the form of a cylindrical slug having at its rear end a head embedded in the other end of said plunger and a bullet nose projecting from said plunger.

13. A relay as defined in claim 5 wherein said first pair of terminals embodies integral loops formed on its end portions within the envelope, each loop embody-- ing spaced parallel legs, one constituting a linear continuation of a respective terminal extending entirely through the respective plug and the other having its end embedded in the plug, said fuse link being in the form of a loop having respective legs anchored at their ends to respective terminal loops and a bight extending into an axial recess which is formed in the adjacent end of the plunger, said plunger having a cross pin extending through said recess and through said bight and engaging the latter to anchor said fuse link to the plunger.

References Cited in the file of this patent UNITED STATES PATENTS 2,216,375 Minter Oct. 1, 1940 2,477,372 Herzog July 26, 1949 2,683,201 Miller et al. July 6, 1954 2,745,930 Reisman May 15, 1956 

